Indeed, but the question asked is whether the coverage is retroactive to travel purchased with another American Express card before the Platinum card account was opened. There is a good argument that it is not, based on the terms:
I think I asked Amex before. Now I'm not 100% certain, but I seem to recollect that travel purchased on an Amex Card before activating the Platinum Charge card would automatically be covered.
The best thing to do would be to call Amex (Axa) and ask them.